Cameras mounted on portable electronic devices such as smartphones each include a flash lens disposed immediately in front of a light source so as to disperse light from the light source. The flash lens is mainly selected from Fresnel lenses, which are ready for reduction in thickness and size.
In an exemplary known method for producing a flash lens, a thermoplastic resin is subjected to injection molding, where the thermoplastic resin is exemplified typically by polycarbonates, poly(methyl methacrylate)s, and cycloolefin polymers (Patent Literature (PTL) 1 and PTL 2). Disadvantageously, however, such thermoplastic resins have low fluidity, cause deficiencies such as unfilled portions and weld lines, and cause poor appearances and/or lower mechanical strengths. In addition, the thermoplastic resins are disadvantageous in working efficiency. This is because molded articles obtained from the thermoplastic resins have poor heat resistance and cannot undergo (endure) board assembly via reflow soldering collectively with other parts or components. Independently, the use of silicones, which have heat resistance, is also known. Disadvantageously, however, this technique suffers from high material cost and poor shape transferability.